Demystifying the 'enlightened machine'

The world of arts and sciences have recently received a big boost on public television. Two extraordinary series made their debuts one after the other last week: The Brain (PBS, Wednesdays, 8-9 p.m.) and Smithsonian World (PBS, Wednesday, 9-10 p.m.). Both shows will be repeated often, so it is essential for viewers to check with local PBS stations for day and time.

''The Brain'' is an eight-part series that tries to unlock some of the mysteries of ''the enlightened machine'' through reviewing the most current scientific theory and research as well as providing a roundup of the various speculations throughout history about the function of the brain.

In order to make this fascinating but difficult material palatable to mass audiences, on-air reporter George Page studies human beings who are coping with brain disorders, thereby personalizing the material. Especially interesting - and poignant - in the premiere episode - is the segment on choreographer Agnes De Mille, who has managed to overcome enormous handicaps due to brain damage.

While the series tries to avoid too much emphasis on medical practices, of necessity because of the subject matter, it treads a ticklishly difficult line between enlightenment, education, and philosophy. Some viewers may be disturbed by what they perceive to be its matter-of-fact scientific orientation.

The second in the series - ''Vision and Movement'' - details how the brain gathers information from the outside world and then reacts to what we perceive. Once again, the dry, scientific material is buttressed by personalization - Greg Louganis tells the secrets of Gold-medal diving and actor Terry-Thomas discusses his battle to control his brain's ''automatic pilot.''

More than five years in the making, ''The Brain'' is TV's most comprehensive look at what Mr. Page describes as ''nature's most mysterious and awesome creation.'' Viewing it will require commitment and focus - it is certainly not easy or ''mindless'' entertainment. Perhaps it is only the beginning of a more profound general awareness of today's evolving knowledge of the complexities of human intelligence.

But what a provocative and stimulating beginning.

On the other hand, ''Smithsonian World's'' premiere special - ''Filling in the Blanks'' - requires less commitment, although it still qualifies as a totally enjoyable, educational experience even as it entertains. It is worth searching for repeats on your local PBS station. The series will air on an approximate bimonthly basis.

The focus is on collecting - from the Smithsonian's great airplane collection to the Freer Gallery's Peacock Room of James McNeil Whistler to the priceless Asian Art of the Sackler Collection soon to be housed at the Smithsonian.

Host David McCullough, the American version of Alistair Cooke, guides viewers through the various collections, stopping now and then for an enlightening interview. He is a perfect electronic host - the man you'd most like to have with you when you visit a museum.

However, when the final segment of the special focuses on Mel Blanc, the man behind the voice of Bugs Bunny, this viewer began to wonder how far afield the special would go. But upon reconsideration, the fact is that Mr. Blanc's memorabilia occupies a place in the Smithsonian itself, so it is difficult to fault executive producer Martin Carr for ''trashing'' the museum. I suspect, however, both the show and the museum are trying just a bit too hard to make themselves popular for mass audiences. The other material is so fascinating that the pop-culture trivia constitutes entertainment overkill, as far as I am concerned.

Perhaps the most unique moment for me came in Dr. Sackler's description of collecting and his belief that art and science go hand in hand: ''Art,'' he says , ''is a passion pursued with discipline; science is a discipline pursued with passion.''

Both the Smithsonian Institution and the James S. McDonnell Foundation should be proud of their association with ''Smithsonian World,'' for it constitutes a unique electronic discipline that pursues the arts and sciences with a fine and admirable passion.